EP0598183A1 - Turbogenerator set - Google Patents

Abstract

In order to provide a power generating installation which comprises a gas turbine (12) with a turbine wheel (22) and a generator (14) with a rotor (30) driven by the turbine wheel (22), and in which the known bearing problems are reduced or even eliminated, it is proposed that the turbine (12) and the generator (14) are combined to form a unit in a housing (10) for the installation. It is further proposed that the turbine wheel (22) and rotor (30) form a rotor unit (26) which rotates as a whole, and that the rotor unit (26) be rotatably mounted in a contactless fashion in the housing (10) for the installation by means of magnetic bearing units (34, 36). <IMAGE>

Description

The invention relates to a power generation system comprising a gas turbine with a turbine wheel and a generator with a rotor driven by the turbine wheel.

In the power generation plants known hitherto, which are used, for example, in the expansion of cryogas or natural gas in order to recover the energy released when the gases expand, a turbine and a generator which is driven but separated from it are usually used.

Since the turbine runs at high speeds and high temperature gradients must also be possible, problems occur in the area of the bearings of the known systems, in particular due to friction and / or leakage and / or contamination of the gas flowing through the gas turbine.

The object of the invention is therefore to create a power generation system in which the known storage problems are reduced or even eliminated.

This object is achieved according to the invention in a power generation plant of the type described in the introduction in that the turbine and the generator are combined in one unit housing to form a unit, in that the turbine wheel and the rotor form a rotor unit which rotates as a whole and in that the rotor unit in the unit housing Magnetic bearing units is rotatably mounted contactless.

The advantage of the solution according to the invention is thus to be seen in the fact that the combination of the turbine wheel and rotor to form a rotor unit rotating as a whole enables a simple construction, and that the use of magnetic bearing units for mounting the rotor unit significantly reduces the friction losses and thus high speeds are possible without any problems and, moreover, the process gas driving the gas turbine is not contaminated by lubricants or contaminants escaping from the bearings.

In principle, the rotor unit can be supported in that the rotor unit is supported by two magnetic bearing units arranged at an axial distance from one another.

For high speeds in particular, it is particularly advantageous if the rotor unit, viewed axially, is mounted on both sides of the rotor, each with a magnetic bearing unit.

In this case, a magnetic bearing unit is advantageously arranged between the rotor and the turbine wheel, so that the turbine wheel is seated on an end of the rotor unit which projects freely above this magnetic bearing unit.

No details have so far been given regarding the design of the magnetic bearing units. An advantageous exemplary embodiment provides that each magnetic bearing unit comprises at least one magnetic radial bearing.

In order to additionally achieve an axial bearing of the rotor unit, it is possible to assign a magnetic axial bearing to one of the magnetic bearing units.

For reasons of a compact construction, however, it is even more advantageous if each magnetic bearing unit magnetically supports the rotor unit against movement of the rotor in opposite axial directions, that is to say that each magnetic bearing unit comprises half of a magnetic axial bearing.

No details have so far been given regarding the type of magnetic storage. It is particularly advantageous if the magnetic bearing through the magnetic bearing units is an active magnetic bearing.

A position control with sensors, which guides the rotor unit in a specific position, is preferably provided for the active magnetic bearing.

In the case of magnetic radial bearings in particular, the bearing is designed such that an axis of rotation of the rotor unit can be defined by actuating the stator of the radial bearings.

In order to realize the high speeds, it is particularly advantageous if the position control selects the center of gravity axis as the axis of rotation for the rotor unit above a certain speed.

In order to obtain an advantageous bearing even at low speeds, it is also expedient if the position control regulates below a certain speed to a geometric axis of the rotor as the axis of rotation.

No details have yet been given regarding the design of the radial bearings. An advantageous exemplary embodiment provides that the radial bearing comprises laminated cores shrunk onto a shaft of the rotor unit and a stand arranged in the system housing.

With regard to the design of the axial bearings, it is advantageous if they comprise a ferromagnetic disk seated on a shaft of the rotor unit and a stand arranged in the system housing.

In order to ensure that the generator is not destroyed when the magnetic bearing units are switched off or in the event of a failure of the magnetic bearing units, provision is advantageously made for the rotor unit to be additionally supported by catch bearings which are effective if the magnetic bearing unit fails. These catch bearings are preferably mechanical bearings, which are designed either as ball bearings or as plain bearings.

In addition, the backup bearings preferably also effect radial and axial mounting of the rotor unit when it is running in the backup bearings and not in the magnetic bearings.

With regard to the design of the system housing, no further details have been given above. An advantageous exemplary embodiment provides that the system housing encloses a turbine interior of the turbine and a generator interior of the generator in a gas-tight manner.

With such a design of the system housing, in particular leakages of the process gas can be controlled particularly advantageously, since leakage gas entering the generator interior cannot flow out in an uncontrolled manner.

It is also particularly advantageous if the system housing also encloses the generator interior in a pressure-tight and gas-tight manner in addition to the turbine interior, so that there is the possibility of keeping the gas present in the generator interior under defined pressure conditions and, by correspondingly lowering the pressure at the required high speeds, the gas friction to reduce.

A particularly advantageous solution provides that a connecting channel through which the rotor unit passes leads from the generator interior to the turbine interior and that the generator interior, the connecting channel and the turbine interior are enclosed gas-tight and pressure-tight by the system housing. In this case, the turbine interior with the connecting duct and the generator interior form a unit which is enclosed as such in a gas-tight and pressure-tight manner, so that on the one hand no problems occur with a leak gas flow from the turbine interior into the generator interior and on the other hand defined pressure ratios can be set in the generator interior in order to achieve the To reduce gas friction and either the leak gas flow from the Suppress the turbine interior into the generator interior by appropriate pressure or to discharge the leak gas flowing from the turbine interior into the generator interior in a defined manner.

In particular, this embodiment of the solution according to the invention advantageously complements the use of the magnetic bearing units, since gas flowing from the gas turbine into the generator and in particular the generator interior is not contaminated by the bearings either in the region of the bearing of the turbine wheel or in the region of the rotor, and in addition the advantages mentioned above occur.

In order to dissipate heat occurring due to the high speeds in the area of the magnetic bearing units, it is advantageously provided that a cooling gas can flow through the magnetic bearing units.

Theoretically, the cooling gas could flow through the magnetic bearing units in different directions. It when the cooling gas flows through the magnetic bearing units essentially in the axial direction is particularly advantageous.

The cooling of the magnetic bearing units can be carried out even more advantageously when a cooling gas flows through the interior of the generator, this cooling gas advantageously flowing through the interior of the generator in a region surrounding the rotor unit and thus flowing superficially along the corresponding sections of the rotor unit.

Any gas can in principle be used as the cooling gas. However, it is particularly advantageous if the cooling gas is identical to the process gas driving the turbine, since in this case a leak gas flow through the connecting channel does not cause any problems and, in particular, does not contaminate the process gas.

The cooling gas used to cool the magnetic bearing units can come from a wide variety of sources. In the simplest case, it is provided that the cooling gas comes from the process gas stream flowing through the turbine.

This can be achieved, for example, in that the cooling gas is the leakage gas flowing from the turbine interior into the generator interior through the connecting channel.

This leakage gas can then be collected and discharged, for example, in the generator interior in an area facing away from the gas turbine.

In order to achieve a defined cooling of the magnetic bearing units, and in particular in the event that the leakage gas coming from the turbine interior does not have a sufficient cooling effect, since this was heated up, for example, before flowing into the gas turbine, it is provided that external cooling gas is supplied for cooling the magnetic bearing units and is discharged again.

The guidance of the external cooling gas through the magnetic bearing units and possibly also through the generator interior can be done in many different ways carry out. For example, it would in principle be possible for the cooling gas to flow in the axial direction either towards the gas turbine or away from the gas turbine.

In particular, if the external cooling gas is intended to supplement the cooling effect of the leakage gas, it is advantageous, however, if the external cooling gas flows through the magnetic bearing units in the axial direction away from the turbine.

A particularly advantageous solution provides that the external cooling gas is supplied between the turbine wheel and the magnetic bearing unit closest to the turbine wheel and flows through the generator interior in the axial direction away from the turbine.

In this case, it is advantageously provided that the cooling gas can be removed from the generator interior on a side facing away from the turbine.

It is particularly advantageous if the cooling gas can be supplied in the region of the connecting channel.

In order to keep the leakage gas flow as small as possible in the event of an excessively high temperature of the leakage gas flow flowing from the turbine interior into the generator interior, provision is advantageously made for a gas flow-reducing element to be arranged in the connecting duct.

This gas flow reducing element is designed, for example, as a non-contact seal, preferably as a labyrinth seal.

As already mentioned above, in order to reduce the gas friction in the generator interior, it is advantageous to keep the generator interior at a defined pressure level.

The pressure level in the interior of the generator is preferably selected so that it is below the pressure at a gas inlet of the turbine.

A particularly advantageous solution provides that the pressure level in the interior of the generator corresponds to a pressure level at a gas outlet of the turbine.

In order to generate as little heat as possible from the generator, which in turn has to be dissipated from the interior of the generator, it is advantageously provided that the generator is a permanently excited synchronous generator.

In particular, it is expedient if the rotor is an electrically passive rotor, so that no current leads have to be fed to the rotor, but only to a stator of the generator.

In order to be able to optimally dissipate the heat occurring in the stator, it is preferably provided that the stator is cooled. For example, the stator could also be cooled by cooling gas, which expediently flows through cooling gas channels provided in the stator. However, it is even more advantageous, in particular because of the better couplings, if the stator is liquid-cooled.

The power generation system according to the invention can be used particularly advantageously if the generator is followed by a converter for generating a customary standardized mains voltage with a standardized mains frequency for a public power supply network, since the generator has an alternating voltage with a strongly changing frequency and the speed of rotation due to the rotor sitting on the rotor unit Generated rotor unit of the appropriate frequency, which is not suitable for feeding into a public network.

In addition, a particularly advantageous field of application of the power generation system according to the invention provides that the turbine is an expansion turbine in order to recover the energy released during the expansion of gases, which can be, for example, natural gas expansion in long-distance lines or gas expansion in cryogenics.

Further features and advantages are the subject of the following description and the drawing of an exemplary embodiment.

Fig. 1

einen schematischen Längsschnitt durch eine erfindungsgemäße Stromgewinnungsanlage und

Fig. 2

einen Schnitt durch einen Rotor längs Linie 2-2.

The drawing shows:

Fig. 1

a schematic longitudinal section through a power generation system according to the invention and

Fig. 2

a section through a rotor along line 2-2.

An embodiment of a power generation system according to the invention, shown in FIG. 1, comprises a system housing, designated as a whole by 10, in which a gas turbine 12 and a generator 14 are combined to form a unit.

The gas turbine 12 comprises a turbine housing 16, which is designed as a gas expansion turbine and has an inlet channel 18 for the process gas to be expanded, which leads to an interior 20 of the gas turbine, in which a turbine wheel 22 is rotatably arranged. From this turbine interior 20 in turn leads an outlet duct 24, in which the expanded gas flows out.

The turbine wheel 22 is part of a rotor unit, designated as a whole by 26, which comprises a shaft 28 carrying the turbine wheel 22 and a rotor 30 of the generator 14 seated on the shaft 28. Thus, when the turbine wheel 22 is driven, the entire rotor unit 26 is set in rotation and thus the rotor 30 of the generator 14 is also driven to rotate about an axis of rotation 32 at the speed of the turbine wheel 22.

The rotor unit 26 is mounted in the system housing 10 in a contactless manner by two magnetic bearing units 34, 36 arranged at a distance from one another in the direction of the axis of rotation 32, the magnetic bearing units 34 and 36 being arranged on both sides of the rotor 30 as seen in the direction of the axis of rotation 32.

Each of the magnetic bearing units 34, 36 comprises a magnetic radial bearing 38, which on the one hand has an annular laminated core 40 shrunk onto the shaft 28 and on the other hand a stator 41 with a stator 42 made of laminated electrical sheets, the poles of which are surrounded by coils 43. Electromagnetically, each stator 42 is divided into 4 quadrants, each with a north and south pole, so that each radial bearing 38 has two active axes, each of which is formed by two opposite quadrants. The weight forces acting on the rotor unit 26 are absorbed by the two upper quadrants of each radial bearing 38, since this radial bearing can only develop tensile forces.

Furthermore, each radial bearing 38 comprises a sensor ring, not shown in the drawing in FIG. 1, the signals of which are evaluated by a position control 44 which controls the axes in such a way that the rotor 26 rotates about the defined axis of rotation 32.

In addition to the radial bearing 38, each magnetic bearing unit 34, 36 also comprises a half 48 of an axial bearing, each half 48 of the axial bearing comprising a ferromagnetic disk 50 seated on the shaft 28 and a stand 52 seated in the system housing 10, in which the windings of an electromagnetic coil 54 are let in.

Each half 48 of the axial bearing acts in such a way that tensile forces are exerted on the ferromagnetic disk 50 by the stator 52, which force the ferromagnetic disk 50 in the direction of the stator 52.

The respective halves 48 of the thrust bearings are arranged in the magnetic bearing units 34 and 36 so that they exert opposing axial forces 56 and 58 on the rotor unit 26 and thus stabilize the rotor unit, the two halves 48 of the thrust bearings also each having sensors and via a common position control 60 are regulated.

Each of the magnetic bearing units 34 and 36 is also additionally provided with a catch bearing 62, the catch bearing 62 being designed as a radial and axial bearing and serving to catch the rotor unit 26 when the magnetic bearing units 34, 36 are switched off or failing and collisions, for example in the To prevent gas turbine 12 or the generator 14.

The position controls 44 of the radial bearings 38 of the magnetic bearing units 34 and 36 are preferably further designed such that they support the rotor unit 26 rotating about their geometric central axis as the axis of rotation 32 below a defined speed. If the specified speed is exceeded, the axis of rotation of the rotor unit 26 is supported as the axis of rotation 32, so that in this state a virtually force-free and self-centered bearing of the rotor unit 26 can be achieved.

In addition to the rotor 30, the generator 14 also comprises a stator 70 and is designed as a permanently excited synchronous generator, the rotor being electrically passive and, as shown in FIG. 2, carrying high-energy magnets 72 which are seated on the shaft 28 and arranged as segments and which are radial are secured to the axis of rotation 32 by a bandage 74.

To cool the stator 70, which in turn carries coil windings 76, the stator 70 is provided with cooling channels 78 which rotate in the stator 70 about the axis of rotation 32 and which are connected to a cooling water supply line 80 and a cooling water discharge line 82 and thus through which cooling water can flow.

The system housing 10 forms, with a first section 90, a turbine housing for the gas turbine 12 and encloses the turbine interior 20 in a gas-tight and pressure-tight manner.

In addition, the system housing 10 forms, with a second section, a generator housing 92, which likewise encloses a generator interior 94 in a pressure-tight and gas-tight manner. The stator 70, the rotor 30 and the magnetic bearing units 34 and 36 are arranged in this generator interior 94. All electrical leads leading in the generator interior are guided through pressure-resistant cable bushings 95.

Furthermore, a connecting duct 96 leads from the generator interior 94 to the turbine interior 20, the shaft 28 of the rotor unit extending through this connecting duct 96 and carrying the turbine wheel 22 on its free end which extends into the turbine interior 20.

In this case, the turbine interior 20 forms a gas-tight and pressure-tight closed space via the connecting channel 96 with the generator interior 94, in which the rotor unit 26 rotates without contact when the power generation system is operating.

In order to throttle a leakage gas flow from the turbine interior 20 into the generator interior 94, a labyrinth seal 98 is also provided in the connecting duct 96, so that only a small part of the process gas flows from the turbine interior 20 into the generator interior 94.

In the simplest case, the leakage gas flow entering the turbine interior 20 into the generator interior 94 serves as cooling gas, which flows through the generator interior 94 in the axial direction away from the gas turbine 12, flowing around the rotor unit 26 and cooling the magnetic bearing units 34, 36.

For additional or alternative cooling of the magnetic bearing units 34, 36, a cooling gas inlet channel 100 is provided, which opens between the labyrinth seal 98 and the magnetic bearing unit 34 facing the turbine wheel 22 and allows cooling gas to flow onto the rotor unit 26 in this area. This cooling gas first flows through the magnetic bearing unit 34 essentially in the axial direction 102, then a gap between the rotor 30 and the stator 70 and then likewise in the axial direction 102 away from the gas turbine 12, the magnetic bearing unit 36 and, like the leakage gas flow, collects in a rear section 104 of the generator interior 94, from which it is discharged via a cooling gas outlet channel 106 and fed to a gas recirculation 108, which supplies the cooling gas to the cooling gas inlet channel 100 again.

The same gas as the process gas driving the gas turbine 12 is preferably used as the cooling gas, so that excess cooling gas can be fed back into the process gas and also from the turbine interior 20 into the Process gas entering the generator interior 94 is not contaminated, on the contrary, the leakage gas entering the generator interior 94 from the turbine interior 20 is also used as cooling gas, the cooling effect of which is optionally supplemented by the cooling gas supplied externally via the cooling gas inlet duct.

The cooling gas is preferably supplied in such a way that there is a pressure in the generator interior which corresponds approximately to the pressure of the process gas in the outlet channel 24 in order to keep the gas friction in the generator interior as low as possible.

The current generated by the permanently excited synchronous generator is finally fed to a converter 110, which converts it into an alternating current with a grid frequency and a grid voltage which allows feeding into a public power supply network.

Claims (34)

Power generation plant comprising a gas turbine with a turbine wheel and a generator with a rotor driven by the turbine wheel,
characterized,
that the turbine (12) and the generator (14) are combined in a unit housing (10) to form a unit, that the turbine wheel (22) and the rotor (30) form a rotating rotor unit (26) and that the rotor unit (26) is rotatably supported in the system housing (10) by means of magnetic bearing units (34, 36) without contact. Electricity generation system according to claim 1, characterized in that the rotor unit (26), viewed axially, is mounted on both sides of the rotor (30), each with a magnetic bearing unit (34, 36). Electricity generation system according to claim 2, characterized in that one of the magnetic bearing units (34) is arranged between the rotor (30) and the turbine wheel (22). Electricity generation system according to one of the preceding claims, characterized in that each magnetic bearing unit (34, 36) comprises a magnetic radial bearing (38). Power generation system according to one of the preceding claims, characterized in that one of the magnetic bearing units (34, 36) is assigned a magnetic axial bearing (48). Power generation system according to claim 5, characterized in that each magnetic bearing unit (34, 36) magnetically supports the rotor unit (26) against movement of the rotor (30) in opposite axial directions. Power generation plant according to one of the preceding claims, characterized in that the magnetic bearing of the rotor unit (26) by the magnetic bearing units (34, 36) represents an active magnetic bearing. Electricity generation system according to claim 7, characterized in that the active magnetic bearing has a position control (44) with sensors which guides the rotor unit (26) in a certain position. Power generation system according to Claim 8, characterized in that an axis of rotation (32) of the rotor unit (26) can be fixed by actuating the stator (42) of the radial bearings (38). Power generation system according to Claim 9, characterized in that the position control (44) selects the center of gravity axis as the axis of rotation (32) for the rotor unit (26) above a certain speed. Power generation system according to one of Claims 4 to 10, characterized in that the radial bearing (38) comprises laminated cores (40) shrunk onto a shaft (28) of the rotor unit (26) and a stand (41) arranged in the system housing (10). Power generation system according to one of Claims 5 to 11, characterized in that the axial bearing (48) comprises a ferromagnetic disc (50) seated on a shaft (28) of the rotor unit (26) and a stand (52) arranged in the system housing (10). Electricity generation system according to one of the preceding claims, characterized in that the rotor unit (26) is supported by catch bearings (62) which are effective if the magnetic bearing unit (34, 36) fails. Power generation plant according to one of the preceding claims, characterized in that the plant housing (10) encloses a turbine interior (20) of the turbine (12) and a generator interior (94) of the generator (40) in a pressure-tight and gas-tight manner. Power generation system according to one of the preceding claims, characterized in that a connection channel (96) through which the rotor unit (26) passes through leads from the generator interior (94) to the turbine interior (20) and that the generator interior (94), the connection channel (96) and the turbine interior (20) are enclosed in a gas-tight and pressure-tight manner by the system housing (10). Power generation plant according to one of the preceding claims, characterized in that a cooling gas can flow through the magnetic bearing units (34, 36). Electricity generation system according to claim 16, characterized in that the cooling gas flows through the magnetic bearing units (34, 36) essentially in the axial direction. Electricity generation system according to one of claims 14 to 17, characterized in that a cooling gas flows through the interior of the generator (94). Electricity generation plant according to one of claims 16 to 18, characterized in that the cooling gas is identical to the process gas driving the turbine (12). Power generation plant according to claim 19, characterized in that the cooling gas comes from the process gas stream flowing through the turbine (12). Electricity generation system according to one of claims 16 to 20, characterized in that the cooling gas is the leakage gas flowing from the turbine interior (20) into the generator interior (94) through the connecting duct (96). Electricity generation system according to one of claims 16 to 21, characterized in that external cooling gas can be supplied and removed again for cooling the magnetic bearing units (34, 36). Power generation system according to Claim 22, characterized in that the external cooling gas flows through the magnetic bearing units (34, 36) in the axial direction away from the turbine (12). Electricity generation system according to one of claims 22 or 23, characterized in that the external cooling gas can be supplied between the turbine wheel (22) and the magnetic bearing unit (34) closest to the turbine wheel (22). Electricity generation system according to one of Claims 16 to 24, characterized in that the cooling gas can be removed from the generator interior (94) on a side facing away from the turbine (12). Electricity generation plant according to one of claims 16 to 25, characterized in that a gas flow reducing element (98) is arranged in the connecting channel (96). Electricity generation system according to one of claims 14 to 26, characterized in that the pressure level in the generator interior (94) is selected such that it is below the pressure at a gas inlet (18) of the turbine (12). Electricity generation system according to claim 27, characterized in that the pressure level in the generator interior (94) corresponds to a pressure level at a gas outlet (24) of the turbine (12). Power generation system according to one of the preceding claims, characterized in that the generator (14) is a permanently excited synchronous generator. Electricity generation plant according to claim 29, characterized in that the rotor (30) is an electrically passive rotor. Power generation plant according to one of the preceding claims, characterized in that the stator (70) is cooled. Electricity generation system according to claim 31, characterized in that the stator (70) is liquid-cooled. Power generation plant according to one of the preceding claims, characterized in that the generator (14) is followed by a converter (110) for generating a customary standardized mains voltage with a standardized mains frequency for a public power supply network. Power generation plant according to one of the preceding claims, characterized in that the turbine (12) is an expansion turbine.

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